Line two cupcake pans with cupcake liners, or spray liberally with cooking spray. (I used a muffin tin so each of the wells is equal to two cupcake wells).
Add the flour, PBfit, salt, baking soda, and cinnamon to a large bowl, whisking to combine.
In a medium sized bowl, mash your bananas with a fork. Add the sugar, mixing to combine.
Add the milk, egg, and vanilla and mix to combine.
Slowly add the flour mixture into the banana mixture until fully combined.
Add the batter to the prepared cupcake pans.
Bake for 25-30 minutes or until a toothpick comes out clean on one of the cupcakes in the center, (closer to 25 minutes for cupcake sized muffins, closer to 30 for larger muffins).